The present invention relates to magnetoresistive heads, and more particularly to a dielectric gap material for use in MR heads and a method for forming the dielectric gap material.
In recent years, there has been a drastic increase in magnetic recording density. As the areal density of the magnetoresitive head increases, the physical size of the head continues to shrink. This trend to smaller head geometry places a great challenge in MR head manufacturing, requiring much thinner and more reliable dielectric gap layers that separate MR sensor stacks from magnetic shields.
Typically, Al2O3 (alumina) is used as a dielectric gap material for MR heads, and is deposited using a conventional sputtering process. Since the sputtering process is a line-of-sight process, the sputtered A2O3 does not provide a good step coverage on the topography of MR sensors. Conventional sputtered Al2O3 gap material only has a step coverage of less than about 35 percent. MR heads often have big topographical changes resulting in steep vertical walls. With the conventional sputtered Al2O3 process, flat areas of the MR head are covered adequately, but vertical or near vertical steps are covered much thinner. The thin coverage can result in reader to shield shorting and a failure of the device.
In addition to providing better step coverage, it would also be desirable for a dielectric gap material to have a higher breakdown voltage and lower leakage current than currently used materials to provide more effective isolation for MR sensor stacks. The increased isolation makes devices more resistant to electrostatic discharge (ESD).
It would be desirable for the process of forming the dielectric gap material to be compatible with currently used MR head manufacturing processes. Conventional chemical vapor deposition (CVD) would not be a good choice for forming a dielectric gap material because of the requirement for a high temperature during the deposition. Conventional CVD to form dielectric films requires temperatures well in excess of 200xc2x0 C. Such high temperatures would ruin an MR head. In order to be compatible with currently used MR head manufacturing processes, the deposition of the dielectric gap material should be performed at relatively low temperatures.
It would also be desirable for the process for forming the dielectric material to not be restricted to line-of-sight deposition. Rather, the process should be performed at pressures above the molecular flow region and should use a high throwing power to produce improved step coverage on difficult three-dimensional topographies.
A silicon nitride dielectric film for use in an MR head according to the present invention comprises from about 38% to 44% by volume of Si, from about 35% to 37% by volume of N, and from about 21% to 24% by volume of H. The dielectric film is formed by plasma enhanced chemical vapor deposition (PECVD) at relatively low temperatures. A plurality of gases capable of reacting to form silicon nitride are introduced into a PECVD reactor. An electric field is generated in the reactor to produce a plasma. The gases in the reactor react in the presence of the electrical field to form a silicon nitride dielectric film.
The PECVD deposited silicon nitride dielectric film of the present invention provides excellent step coverage, high breakdown voltage and a low leakage current. The process for forming this silicon nitride dielectric film is compatible with currently used MR head manufacturing processes because relatively low temperatures may be used during the deposition.